A test of Equation References

Here is a labeled equation:
$$x+1\over\sqrt{1-x^2}\label{ref1}$$
with a reference to ref1: \ref{ref1},
and another numbered one with no label:
$$x+1\over\sqrt{1-x^2}$$
This one uses \nonumber:
$$x+1\over\sqrt{1-x^2}\nonumber$$

Here's one using the equation environment:
\begin{equation}
x+1\over\sqrt{1-x^2}
\end{equation}
and one with equation* environment:
\begin{equation*}
x+1\over\sqrt{1-x^2}
\end{equation*}